A number of products formed of polymeric material, generically referred to as plastic, are utilized out of doors where they are exposed to various weather conditions, particularly to sunlight. The ultraviolet radiation in sunlight has a deleterious effect on the surfaces of such products causing them to become discolored and crazed to the point where the surface is unattractive. In the case of certain products, particularly transparent products used as aircraft and vehicular windows and windshields, exposure to sunlight and other weather conditions can cause a substantial loss in transparency requiring replacement of the window or windshield. Various methods have been available in the prior art for refinishing "plastic" surfaces that have become weathered. Basically these methods include the use of combinations of various solvents which remove scratches and weathered surface material and restore the surface of the article.
For example, U.S. Pat. No. 4,322,861, Franz et al, discloses a method for improving and restoring the surface of plastic transparencies by coating the surface with a clear high gloss polymer, preferably made of a fast curing acrylic, polyurethane or epoxy resin.
U.S. Pat. No. 4,133,912, Stuart, similarly discloses a method for refinishing thermoplastics by cooling the body of the article to be refinished, spraying the surface with a solvent which dissolves and reforms the immediate surface of the body but does not attack the underlying material.
U.S. Pat. No. 4,301,193, Zuk, relates to a process for restoring clear plastic articles which involves a polishing formulation containing a mild abrasive to the surface to be treated and polishing the surface to remove scratches and dirt therefrom. Following the polishing operation a coating of liquid silicone is applied on the surface and wiped off to remove residual dirt and leave behind a thin layer of the silicone which fills the microscopic imperfections in the surface caused by the polishing.
U.S. Pat. No. 4,374,745, Sibley, relates to a cleaning composition for glass and plastic, particularly optical glasses and plastics which is a gel which includes a preservative and a cleaner and may further include an anti-fogging agent.
While the foregoing methods may be suitable for restoring the transparency and surface condition of a plastic article, it is clear that these prior art compositions and methods do little to improve the resistance to weathering of the treated surface of the article and thus while the surface may be temporarily restored, the weathering effect will become more and more pronounced over a period of time and will eventually require replacement of the article.
Accordingly, it would be highly desirable to have a method for enhancing the weatherability of plastic articles, such as signs, windows, outdoor furniture and the like, which both enhances and restores the surface of the product and also makes the surface more resistant to the effects of sunlight, particularly ultraviolet radiation which has a deleterious affect on plastic articles. It would also be desirable to have products produced from plastic materials which are designed to be used out of doors and which have a surface having improved resistance to ultraviolet radiation.